1. Field of the Invention
The present invention relates to an image projection system, an image projection method, and an image projection program embodied on a computer readable medium. More particularly, the present invention relates to an image projection system which projects an image onto a projection surface, and an image projection method and an image projection program embodied on a computer readable medium which are executed by the image projection system.
2. Description of the Related Art
In a conference or the like, an image of an explanatory material may be projected onto a projection surface when giving an explanation. Recently, it is often the case that data of an explanatory material is stored in a computer in advance, and a projector, for example, serving as a display device is connected to the computer so as to cause the projector to display an image of the material output from the computer.
Japanese Patent Laid-Open No. 2006-235158 discloses a projection system wherein an image of a projection surface onto which an image has been projected from a first projector is picked up, a compensation parameter for cancelling a color pattern on the projection surface is generated, and a compensation image generated on the basis of the compensation parameter is projected onto the projection surface from a second projector. This projection system is able to project an image as close in color to one projected onto a white screen as possible even when a projection surface has a color pattern.
On the other hand, when a whiteboard on which a character or a graphic can be drawn is used as a projection surface for a projector, an image may be drawn superposed on the image that has been projected. In this case, however, if a background of the image projected onto the whiteboard is similar in lightness to the image drawn on the whiteboard, a viewer may have difficulty in recognizing the drawn image. Further, in the case where a character or a graphic in the drawn image is superposed on a character included in the projected image, the character in the projected image may be hard to be distinguished. Still further, in the case where images of two or more pages are being projected, when a projected image is switched from a first page to a second page after an image has been drawn on the first page, a newly projected image for the second page will be superposed on that image drawn for the first page and left on the whiteboard, causing the projected image of the new page to be hard to be recognized. The conventional projection system described above has not taken such problems into consideration.